Subnetting Question

Unanswered Question
Oct 30th, 2008

In subnetting, when a question asks to configure the router with the last IP in the 4th usable subnet, what exactly are they looking for? For example, in a Class B network 130.4.0.0 /30 (subnet 130.4.4.0 has already been assigned and is unavailable), would the answer be 130.4.12.2 or 130.4.16.2? I hope this makes sense.

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Richard Burts Thu, 10/30/2008 - 09:49

Brandi


The logic here is not clear. Is the statement that subnet 130.4.4.0 has already been assigned and is unavailable from the question, or is that your editorial comment?


Also if they give network 130.4.0.0 and subnet mask of /30 then the subnet options would be 130.4.0.0, 130.4.0.4, 130.4.0.8, 130.4.0.12, and 130.4.0.16.


In classical subnetting the .0 subnet is reserved and therefore the fourth usable subnet would be .16.


HTH


Rick


bnturnbo1 Thu, 10/30/2008 - 11:19

You're right. My mistake. The mask is actually 255.255.252.0. And the subnet 130.4.4.0 has already been assigned to another device and can't be used.

pkaretnikov Fri, 10/31/2008 - 00:00


In subnetting, when a question asks to configure the router with the last IP in the 4th usable subnet, what exactly are they looking for? For example, in a Class B network 130.4.0.0 /30 (subnet 130.4.4.0 has already been assigned and is unavailable), would the answer be 130.4.12.2 or 130.4.16.2? I hope this makes sense.


Assuming that you are looking for the 4th subnet of 130.4.0.0 /22 , the network is 130.4.16.0. The last IP in that subnet is 130.4.19.255 which is the broadcast. The highest usable IP would be 130.4.19.254.

vishvajeetsingh Sat, 11/08/2008 - 05:00

This will be the correct answer, if u dont use "ip subnet-zero" command, otherwise answer should be - 130.4.15.254/22.



Cheers

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